Compressed fuel units of diisopropylideneglyoxal



produces ir Patented July 22, 1952 COMPRESSED FUEL. UNITS, orDIISOPROPYLIDENEGLYOXAL Murray Berdick, New York, and HaroldR;Ho'chstadt, Brooklyn, N. Y., assignors to the United States of Americaas'represented by the Secretary of the Army No I )rawihg. ApplicationNovember 4, i949, Srial No. 125,646

tice with the invention, thesam'e being realized and attained'by meansof the processes; steps, and combinations pointed out in the appendedclaims.

The invention consists in the novel steps, processes, combinations andimprovements herein shown and described;

Various materials have been suggested and used for this general purposein the past. They all, howeven, have disadvantages of varying degrees.

solidified alcohols, such as thefamiliar Sterne, have been used, butthese require packaging, in

heavy'cans because they are not true solids but soft gels usuallycontaining some liquid.- Consequently, their emciency in terms of heatdelivered per unit weight of package is severely impaired. Further, ifthe canis allowed to stand open at room temperature, volatilization ofthe alcohol occurs quite rapidly; for example, up to 55% loss in weightin 19 hours.

Combustible solid Waxes have been used. but these have a highluminosity, an obvious military disadvantage, and they soften and flowat elevated temperatures. They arequite diflicult to ignite and,therefore, usually require a' wicks-r a fuse and they usually produce acridodors'and deposit a considerable amount of soot.

Hexamethylene tetramine has been usedand was produced commercially underthe trademark He'atab, and was also usedby the military forces ofGermany Englandy and other nations. This c m e hp 'e er is sno n. apears highly sex-1c nitrogencontaining 'furnes during burningi ltis verysolubleirr water an d it" has beenfound t at-,- when-sit s stored 150;;aimont 1150 F a has "lost over 25 in we'ight bysuolime-mom 1 oMetaldeh-yd cleposits considerable soot and ting fumes when burned? Onstorage for arnonth at 150 FL it loses' almost 30% of its weight:Paraformaldehyde is" soluble-in water and is" completely volatiliaedafter four days of storage at 150 When burned'it'p'r'd duces a-veryunpleasant and irritating odor.

Trioxan'ei is soluble in water. re rse arsonlimatiorr (completevolatilizat'ion'in two-days at room temperature)" isso high that itmustbe packed in elaborate and expensive foil sealed packages. Theobnoxious-lodor'pf formaldehyde is often noticed during burning. IAllthese' materialsfall short ofthe require- 11 Claims.

2 ments for an ideal fuel unit of the type herein contemplated. Theserequirements are as follaws 1'. Through the temperature range liable tobe encountered during storage and shipment (minus F. to plusl50 F.),the, fuel units must be chemically stable; remain solid, lose virtuallyno weight by sublimation, not be affected by water or water vapor, andbe resistant to breaking if dropped.

2. From the manufacturing point of view, the fuel must be low in cost,require no heavyor expensive protective packaging, be formed readilyinto convenient sized tablets by casting, extrusion, cutting orpressing.

3. From the point of View of combustion, the fuel must be capable ofready ignition by a single safety match regardless of the ambienttemperature; for example, as low as F. It must burn with' a fiarne thatdoes not deposit a substantial quantity of soot on the surface beingheated must notyield products of combustion which are highly toxic orirritatingi -It must burn with aavind-resistant flame and, if it is to"be used for military purposes, it must burn with a non-luminous flame inorder to avoid observation'alnd detection by the enemy. It must deliverenoughh'e'at so that a small quantity of fuehfor example, 2 ounce iscapable of heating an i'ric livld'ual portion of food to a palatabletemperature. It must burn at arate which will not bu n food, yet fastenough to be practical, and must retain its form or shape during burningand not flow; I

An object of we: present invention is to provid a composition whichovercomes all the disadvantages of the prior art fuels, and which meetsevery one of the requirements which have been enumerated above for anideal fuel unit. We have found that diisopropylideneglyoxal, hereinafterreferred to as D-IPG, when,- admixed with a' suitable supporting agent,meets every requirement listed above.

DIPG' has been synthesized before, but no practical use for it has everbeen suggested. Fischer and Taube .report its synthesis in Beri'chte'592854" (1926)". Raudnitz reports the synthesis in' J. Chem. Soc.(London), page 763 (1948) and reports amelting point of 207 C. andassigned the-following empirical and structural formulae: CmHia'Os IIIThere has been some controversy in the literature over the correctassignation of structure but, for our purposes, it i not necessary toresolve that problem. It is sufficient to know that, using the method ofRaudnitz, we have synthesized from glyoxal sulphate and acetone, in anexcess of acetone, a compound which has a sharp melting point at 206-'7C. and an analysis as follows:

i g i for Analysis Percent Percent 049.66 049.82, 49.75 H621 H6.6l, 6.53

This compound is a white solid which crystallizes in plate-like form andhas a somewhat waxy feel. It is not only insoluble in water but isactually hydrophobic.

The DIPG is admixed with from about 1% to about 15% by weight of asupporting agent, and preferably about 3% by weight of a supportingagent of a cellulosic, carbonaceous or siliceous nature or combinationthereof.

Virtually any form of cellulose will act as a v supporting agent forDIPG. For convenience of uniform incorporation, it is desirable to use afinely divided cellulose flock. Satisfactory compositions are obtainedwith fibers having an average length under 2 mm., but this size is notcritical. In order to eliminate odor, smoke or residue from the fuel thecellulose must be of high purity. Preferred celluloses have an ashresidue of less than 0.5% and are contaminated with less than 0.5% ofmaterials such as lignin, inorganic salts, and the like. A highalphacellulose content (about 95%) is desirable.

An example of a particularly useful cellulose is that availablecommercially under the name Solka-Floc SW-40A (Brown Co.). Themanufacturers specifications are that it consists of pure, soft, white,strong, absorbent, finely divided, chemically purified, wood cellulosefibers in an easy-to-handle flock form. The average fiber length is 165millimicrons. The alpha-cellulose content 'is 94%, the remaining 6% issubstantially betaand gamma-cellulose and the ash is 0.3%.

The carbonaceous materials to be used as supporting agents are thosehaving a high capacity ture with. DIPG, it is desirable that the carbonbe in a powdered form, rather than in a granular form. Preferably 98% ormore of the carbons should pass through a 50-mesh screen.

In the preferred form of carbon powder, it is not sufficient for theratio of surface to volume to be high. Certain charcoals and activatedcarbons, which have a high adsorptive capacity for gases, do have a veryhigh surface to volume ratio. These materials, however, arecharacterized by a structure having very many more pores of very smalldiameter. Such a structure, which is exhibited by cocoanut charcoal andnumerous commercial products designed for use in gas masks,air-conditioning systems, solvent vapor recovery systems and the like,makes the carbon not particularly suitable for use with DIPG.

The most preferred forms of carbon are set forth in the following threegroups:

1. Carbon blacks. These materials are also known as gas blacks, naturalgas blacks, ebony blacks, jet blacks, hydrocarbon blacks, satin glOSSblacks, and silicates of carbon. They are normally the product ofincomplete combustion of gas, deposited by contact of the flame on ametallic surface. Structurally, they are considered to be mainlycrystalline, blended with some amorphous particles. They are usuallyhard and brilliant. An example of a useful material in this group isSuper Spectra Black (Binney and Smith 00.). It is a high color carbonblack pigment with a particle size between 10-20 millimicrons. A sludgeof the carbon is reported to have a pH of 5.2. Chemisorption of diphenylguanidine is reported to be about 3 moles per gram X 10 The oil sorptionvalue is reported to be 28. The surface available is reported as over 22acres per pound; the tinting strength as 99.

2. Acetylene blacks. These materials, formed by the decomposition ofacetylene, are not useful either as gas adsorbents or decolorizingagents.

Their principal uses are in plastic and rubber compounding, and inmaking dry cells. An example of a useful material in this group isShawinigan Acetylene Black (50% compressed) which is made by the thermaldecomposition of acetylene. As deduced from X-ray diffraction andelectron micrograph studies reported in the literature, the particlesare composed of many crystalline zones (micelles or crystallites) inrandom orientation. The particles are joined together in a chainlike orfibrous fashion so that the mass of the black has a three dimensionalfishnet structure. The following properties have been reported:

Shawinigan Black will not sustain its own combustion, but will glow ifignited in the presence of substantial amounts of other materials. It isnot readily wet with water, but has an extremely high absorptioncapacity fororganic liquids.

3. Vegetable decolorizing carbons. These carbons, which have a largerparticle size than the two preceding groups, may be made in many ways.Their effectiveness as supporting agents depend to some extent on themethod of manufacture, because porosity and compactness depend on theconditions under which carbonization has been effected. Decolorizingchars made by carbonization of lignite are especially useful; those madeby carbonization of paper-mill waste liquors are less effective. Alldecolorizing carbons are activated after carbonization. They are softchars which appear as black glistening powders.

An example of a useful material in this group is Darco G-GO (DarcoCorp), which is made by carbonization of lignite, then activated by airand steam. It has a somewhat granular structure under the microscope,and is reported tohave the following properties:

Carbon 93-96% Ash 3-6%. HCl-soluable portion 0.20% pHof water extract5.6 Density (loose pack) 17.9 lb./cu. ft. Density (so-lid pack) 2225lb./cu; ft. Screen analysis (Per cent) through 200 40.5

Useful siliceous materials are silicas having 95% or more of theparticles with diameters below 40 microns. The preferred silicas arethose in which substantially all of the particles have diameterssubstantially below microns. Two such preferred silicas are aerogelsilica andfumed silica. Silicas of high purity (over 90% SiO2) aredesirable. A commercial example of a preferred silica is Linde Silica(Linde Air ProductsCo.) which is an amorphous fumed silica (99.9% S102),a white powder witha maximum particle diameter of 0.05 micron. 7

The following examples will serve to illustrate typical embodiments ofthis invention, In each example an intimate mixture was made of the dryingredients and this mixture was then formed into pellets by pressing at6000 p. s. i., at room temperature. The proportions. given are parts byweight.

Example 1. Composition:

DIPG 9'7 Solka-Floc SW-A 3 The pellets were smooth and firm. Ignitionwas easy with a single safety match, even immediately after' storing apellet for several hours in a cabinet kept at sub-zero temperatures withDry Ice. The pellets burned with substantially non-luminous flames andno smoke. They deposited very little soot on asurface being heated. Ahalf-ounce pellet heated one pound of water from 77 F. to 173 F. in 8.0'minutes. The amount of ash was very small. On storage at 150 F., apellet had lost only 1% in weight after three weeks.

Example 2 Composition:

DIPG 97 Super Spectra Black 3 The pellets were very tough and smooth.They ignited easily, burned with a substantially nonluminous flame, andleft only a small residue. The pellets retained their shape whileburning.

Example 3 Composition:

DIPG 97 Linde Silica 30 3 This composition formed a good, smooth, firmhard pellet. It ignited readily, burned with a substantiallynon-luminous flame, did not char or flow during burning.

Example-4 Composition:

DIPG 97.0

Darco (i-60 1.5 Solka-Floc SW-40A 1.5

Thepellets were tough and smooth. They did not shatter when dropped.They could be lit easily with a safety match, and burned with asubstantially non-luminous flame. The pellets retained their shape anddid not flow during burning.

Example 5.

Composition:

DIPG a..- 97.8 Darco G-60 2.0 Solka-Floc SW-40A 0.2

The pellets were tough and smooth. They were unaffected by immersion inwater. They were stable and solid at F. They ignited readily and burnedwith a substantially nonluminous flame. They showed only slight viscousflow during burning. There was no smoke.

Example 6 Composition:

DIPG 98 Shawinigan Acetylene Black (50% compression) 2 The pellets weresmooth and shiny. They ignited readily and burned with a substantiallynon-luminous flame. The pellets retained their shape, and showed no flowduring burning. Therewas a minimum of smoke, odor, or unburned residue.

Example 7 Composition I DIPG 97.5 Darco G-60 1.5 Shawinigan- AcetyleneBlack (50%. compression) 1.0

The pellets were tough, smooth, and shiny. Theyburned in a mannersimilar to those of Example 6. i

One pellet of this composition was ignited in a wind tunnel, andsubjected to gradually increasing air velocity. The flame was notextinguished until the wind had reached a velocity of 25-26 milesper'hour.

We have also found that DIPG, with an ad mixed" supporting agent, whencompressed, gives asurfa'ce which permits coating, for example, byspraying or dipping. This permits us to impart to the fuel tabletscertain characteristics which may be desired. For example, it maybedesirable to coatthe tablets with a flammable, film-forming materialsuch as nitrocellulose for easier low temperature ignition. Such acoating also serves to prevent the carbonaceous type of supporting agentfrom being deposited on the hands and clothing of the user.

Example 8 After pellets of the composition of Example 7 were molded asusual, they were sprayed over their entiresurfaces with a solutionhaving the following composition:

Nitrocellulose (RS grade, second viscosit 5.0 DIPG 1.2 Acetone 25.0Methyl isobutyl ketone 68.8

When the solvents had evaporated, the coating on an B-gram tabletweighed 0.04 gram. The pellets had a smooth, polished appearance, andwere hard, firm, and non-friable. There was no tendency for carbon tosmudge on the fingers when the pellets were handled.

We found that pellets treated in this manner ignited readily with apaper safety match, even at sub-zero temperatures. The flame spread overthe surface more rapidly than in the case of an uncoated pellet. Thefuel burned with a substantially non-luminous flame, giving nonoticeable odor during burning.

Example 9 Composition DIPG 90 Darco G-60 -1 Solka-Floc. SW-40A 5 Thpellets were 'shiny and slightly. friable. They ignited readily andburned with a substantially non-luminous fiame. They retained theirshape and exhibited no flow during burning. Slight intermittent sparkingwas noticed during burning. After the fuel was consumed, the smallresidue glowed and emitted slight smoke and odor.

Example 10 Composition:

DIPG 85 Shawinigan Acetylene Black (50% compression) The pellet Wassomewhat friable. Itwas ignited very readily with a safety match. Thefuel burned with a substantially non-luminous flame. There was no flowduring burning. A certain amount of smoke and odor were emanated duringburning. There was a considerable unburned residue.

In most instances, as the percentage of admixed supporting agent isincreased, the efficiency of the fuel is decreased, while the smoke andodor are increased. Thus a minimum of suppropylideneglyoxal as the majorconstituent of said fuel unit and from about 1% to about 15% by weightof a supporting agent admixed with said diisopropylideneglyoxal, saidsupporting agent being substantially non-luminous and substantiallynon-smoke-producing on combustion of said diiso'propylideneglyoxal.

2. The fuel unit of claim 1 wherein the supporting agent is present inan amount of about 3% by weight.

3. The fuel unit of claim 1 in the form of a compressed tablet having acoating of nitrocellulose.

4. A compressed. fuel unit comprising diisopropylideneglyoxal as themajor constituent of said fuel unit and from about 1% to about 15% byweight of a supporting agent admixed with said diisopropylideneglyoxal,said supporting agent being a member of the group consisting of finelydivided solid cellulosic material, solid carbonaceous material having aparticle size of less than 400 millimicrons, and finely divided soliddecolorizing carbon material.

5. The fuel unit of claim 4 wherein the supporting agent is carbonaceousmaterial having a particle size of less than 400 millimicrons.

6. The fuel unit of claim 1 wherein the supporting agent is adecolorizing carbon.

7. The fuel unit of claim 4 in the form of a compressed tablet having acoating of nitrocellulose.

8. The fuel unit of claim 5, wherein the supporting agent is carbonblack.

9. The fuel unit of claim 5, wherein the supporting agent is acetyleneblack.

10. The fuel unit of claim 4 wherein the supporting agent is cellulosic.

11. The fuel unit of claim 1 wherein the supporting agent is siliceous.

MURRAY BERDICK. HAROLD R. HOCHSTADT.

REFERENCES CITED The following references are of record file of thispatent:

Raudnitz, Chem.- Abstracts, vol. 42, p. 8162 (1948).

in the

1. A COMPRESSED FUEL UNIT COMPRISING DIISOPROPYLIDENEGLYOXAL AS THEMAJOR CONSTITUENT OF SAID FUEL UNIT AND FROM ABOUT 1% TO ABOUT 15% BYWEIGHT OF A SUPPORTING AGENT ADMIXED WITH SAID DIISOPROYLIDENEGLYOXAL,SAID SUPPORTING AGENT BEING SUBSTANTIALLY NON-LUMINOUS AND SUBSTANTIALLYNON-SMOKE-PRODUCING ON COMBUSTION OF SAID DIISOPROPYLIDENEGLYOXAL.